There's an awful lot of propoganda about ecstacy, so I can understand why you're getting conflicting reports. I'm going to try and explain what happens in the brain with these drugs in the hope that it will clear things up for you.

Prozac is an SSRI--a selective serotonin reuptake inhibitor. It interferes with your neurotransmitters in such a way that you end up with more serotonin (a chemical that, among other things, makes you feel good). Ecstacy does all kinds of crap in your body, but mainly it also interferes with your neurotransmitters in such a way that you have an increase in serotonin.

So the net result of using both of these drugs is that you end up with a lot of serotonin. Way too much. And in this case, too much of a good thing is definitely a bad thing. At first your friend will feel nice and high...and then (most likely) serotonin syndrome will kick in. Her mental state will shift rapidly (from happy to God knows what), then probably some hyperthermia, seizures, lack of motor control...and then possibly death. (If someone helps her right away, they'll have a better chance of surviving, but they'll end up spending some of the most excruciating hours of their life in an emergency room. Of course, a lot of times at these raves everyone else is high and unable to drive anyone anywhere. Or, they're afraid of calling an ambulance because they fear getting the police involved.)

In your position, I would do whatever I could to stop them from taking these drugs. (In fact, I'd probably call the cops to break up the rave before I let the friend risk death so foolishly like that.)